Airplane interphone set



Feb, 26 1924. 1,484,973

G. H. STEVENSON AIRPLANE INTERPHONE SET Filed Dec. 11 1919 PatentedFeb. 26, 1924.

"UNITED sT -rss PATENT I OFFICE.

GEORGE H. srnvnnson, or'aYn, New YORK, ASSIGNOR TO wns'rnnn ELECTRIC OOM- PANY, mooaroanrnn or NEW Yonx, N. Y., A CORPORATION or NEwYoR-x.

AIRPLANE INTERPHONE sn'r.

Application filed December 11, 1919. Serial No. 344,107.

T all whom it may concern:

Be it known that I, GEORGE H. STEVENSON a subject of the King of Great Britain, residing at Rye, in the county of Westchester, State of New York, have invented certain new and useful Improvements in Airplane Interphone Sets, of which the following is a full, clear; concise, and exact description.

This inventionrelates to airplane interphone sets and moreparticularl'y to intercommunicating sets for wire'signaling, one 7 or more of which are also associated with radio signaling apparatus. I

'An object of the invention isto provide apparatus to permit an occupant of an airplane to keep in constant communication with a distant signaling station on another 7 airplane or on the ground and at the'same time .to be able to receive communication from other occupants of the airplane.

. Another, object of the inventionis to provide a circuit arrangement in which an aviators headset may be used for both interphone and radio communication.

A further object of the invention is to provide a combined radio and interphone system with common repeating and amplifying elements, for both the radio and intercommunicating circuits.

According to this invention, an airplane pilot and the observer are each equipped with headsets interconnected to permit communication during flying. A radio'receiving apparatus including an amplifying re,- peater is also associated with the headsets in such manner that the repeater islcommon to both the radio receiving circuit and the interphone circuits. A radio transmit ting apparatus is placed under the control of the observer. The observer is therefore able to carry on two-way communication with a distant radio station .or two-way convers'ation with his pilot, the same receiving amplifier serving for either conversation. The observer operates a switching arrange ment which controls the'high frequency radio transmitting circuits and thus connects the antenna either to a radio receiving branch when listening,' or to a radio transmitting branch when talking.

Other objects of the invention will appear from the following detailed description taken in connection with the drawing which illustrates diagrammatically a combined rawhich are normally open.

dio and interphone signaling apparatus for an airplane.

Referrmg to the drawing, a conventional antenna 1 having a transmitting branch 2" and a receiving branch 3 is shown normally connected by a remote control switch 4 to receiving branch 3. Coupled to the receiving branch is a detector D preferably of the thermionic type, to which is connected a thermionic repeater or amplifier A. A'pilots set indicated by the rectangle P and an observers set indicated by rectangle 0 each include a high resistance receiver R connected in the output'circuit of amplifier A.

Associated with transmitting branch 2 of the antenna by means'of a modulator 'M,

is a source-5 of carrier frequency current.

The modulator may be of any conventional type operating in the ordinary manner when subjected to carrier current electromotive forces and low frequency impulses to trans"- m t carrier frequency currents modified. in ELCCOIdfiIlCG'W lth thelow frequency impulses.

Low'ifrequency speech currents or impulses are impressed upon the modulator M from a talking circuit 6 which may be energized by a talking battery 7 under the control of "an observe'rs transmitter 8 througha normally closed contact 9 of two-way interphone switch 10 and the right contact of double contact radio switch 11. As illustrated, the contacts of radio switch 11 are normally open. Either of these switches may take the form of push-buttons or switches of any other convenient type. A remote control relay 12 in series with an energizing 'source 13 and normally open left contact of radio switch 11 serves, when energized, to

l from receiving branch 3 and to connect it to transmitting branch 2. Connectedin shunt to the output'circuit of detector D is a path including a high resistanceele ment' 14: and the secondary winding of a transformer 15, the primary winding of of the primary winding of transformer 15 is connected to the normally open contact of interphone switch 10 and thiswindmg may therefore be connected to talking bat- One terminal operate switch l to disconnect the antenna tery 7 and transmitter 8, by closing interphone switch 10 on its normally open contact. An ai'nplil'ication shunt resistance 18 is connected across the receiversR to reduce the response in the receivers and this shunt may be opened at switch 19 under the con trol of the observer to increase the receiver response.

In normal operation, switch A connects the antenna 1 to branch 8, switch 11 and key 17 are open and interphone switch 10 is closed on the left or radio contact, as shown. Since the 'adio t 'ansmitting apparatus is electrically disconnected from the antenna, no energy is being radiated and the receiving apparatus is undisturbed by oscillations from source 5. Radio signaling oscillations from distant stations are received and detected and the detected signal currents are amplified by amplifier A and supplied to receivers R of both the pilot and the observer. If the pilot desires to speak to the observer, he closes his cut-in key 17 and talking currents are impressed by trans former 15 upon the output circuit of detector D and after amplification are supplied to both receivers R, thus furnishing side tone in the pilots own receiver and transmitting speech currents to the receiver of the observer. To respond to the pilot, the observer closes interphone switch 10 on its right contact thus establishing a talking circuit from transmitter 8 through the winding of transformer 15. In this manner conversation between the observer and pilot may be carried on without radio transmission. By means of the amplifier A and the shunt resistance 18, the desired strength of signal may be secured. Cut-in key 17 is normally open to prevent unnecessary waste of talking battery energy and to prevent transmission of noises picked up by the transmitter 16 particularly during periods when the radio signals are being received.

If the observer desires to transmit to the distant radio station, he closes radio switch 11 and the left contact of this switch completes an energizing circuit for remote control relay 12, thus operating switch t to connect the antenna to the transmitting branch. The right contact of radio switch 11 closes a talking circuit 6, enabling voice currents to be impressed upon modulator M, together with carrier current from source 5. As is well understood, the carrier current modified in accordance with speech will be supplied to the antenna 1 from which correspondingly modified oscillations will be radiated. hen the observer stops talkin he permits switch 11 to return to its normal open position, thus disconnecting the antenna 1 from the transmitting branch and connecting it to the receiving branch. During radio conversation between the observer and the distant station, the pilot hears the received signals as previously explained. When the observer is talking to the distant radio station, the induction of the radiated energy upon the receiving branch is sufiicient to give a certain response in the receiving set furnishing side tone to the observer and the pilot is permitted to listen in on the conversation. The pilot may, at any time, close key 17 and talk to the observer regardless of whether the antenna is connected for receiving or transmitting, since his talking circuit is entirely independent of the antenna and its switching circuits. It is therefore possible for the observer to keep in communication with the distant radio station and be instantly called by the pilot it necessary- The single amplifier serves for both radio andinterphone operation and considerably simplifies the apparatus.

The pilots set and the observers set are, of course, interchangeable depending upon which it is desired to keep in communication with the distant radio station.

Although this invention is particularly applicable to airplane radio operation and has been so described, it is to be understood that it is equally suitable for intercommir nicating sets on any craft or even in a stationary land station. For carrier current transmission, the antenna may be replaced by a transmission line as is now well understood. In certain broad aspects, the invention is not limited to high frequency signaling but includes various combinations of transmission line apparatus and'interphone circuits.

l/Vhat is claimed is:

1. A transmission system comprising a one-way repeater, a circuit for supplying thereto message impulses received from a distant point, two local stations comprising receiving devices associated with said repeater and one winding of a transformer and transmitting devices associated with another conductively independent winding of said transformer, said repeater being in fixed relation to said local stations whereby two-way communication is permitted between said local stations.

2. A radio receiving system including an amplifier, a local receiving signaling set connected to said amplifier for receiving radio signals, a second local signaling set, said amplifier connecting said signaling sets for two-way communication.

3. An airplane signaling system comprising intercommunication apparatus, two 10- cal signaling stations, a repeater associated with said radio apparatus and said intercommunication apparatus by means of a transformer having conductively independent windings to enable two-way intercommunication between said stations.

4:. A radio receiving apparatus including a detector and an amplifier in cascade and a two-way intercommunicating circuit connected to said amplifier whereby said amplitions, means. including a single amplifier connecting said stations for two-way signaling, and a variable resistance shunt across the receiving devices of said stations under the control of an operator at one of said stations whereby the amplitude of the received signaling currents may be regulated at will. I

6. A transmission system comprising a one-Way repeater consisting of a demodulator and an amplifier, a receiving circuit,

two local stations, receiving devices at said local stations connected to the output circuit of said amplifier, a transformer having. two conductivelyindependent windings, one of said windings connected across a portion of the output circuit of said demodulator,

the other winding connected to transmitting devices on said local stations whereby two- Way communication may be obtained between one of said local stations and the other station or said distant point.

7. In combination, two signaling stations each comprising a transmitter and a receiver, means for modulating a carrier Wave in accordance with signal currents, a one way repeater, means connecting said re 'peater and said stations to permit two-way communication between said stations through said repeater and switching means to permit an operator to disconnect one of said transmitters from said repeater and to connect it to said modulating means.

In witness whereof, I hereunto subscribe my name thls 8th day of December, A; D., 1919.

GEORGE H. STEVENSON. 

